Many devices may be located on an optical pickup unit (OPU) of a recording/reproducing apparatuses (such as DVD and CD drives, DVD camcorders, DVD video recorders, etc.). Such devices can include, e.g., a laser diode driver (LDD), a power monitor integrated circuit (PMIC), and a photo-detector integrated circuit (PDIC). Conventionally, many aspects of such devices were not programmable after the device was placed on the OPU. Or if they were programmable, were only capable of being programmed once. However, as more and more types of media and standards exist, and manufacturers desire that the same devices can be used with the different types of media and standards, there is a desire that the devices on an OPU can be programmed by a controller that is located on a main board connected to the OPU via a flex cable.
There is also a desire to minimize the number of wires of the flex cable. Accordingly, it has been suggested that serial lines can be used to program at least one device on the OPU. For example, there exist some LDDs that include a serial interface, which can be used to program the LDD. More specifically, three serial lines, including a serial enable (SEN) line, a serial clock (SCLK) line and a serial data input/output (SDIO) line, which are part of the flex, have been used to write data to and read data from registers of LDDs. However, there is now a desire to program more than just the LDD.
One solution would be for each device to have their own dedicated serial lines. However, this would result in the flex cable including too many wires, which is undesirable, and often unacceptable. Another possible solution would be for each device to share the same serial clock and data lines but have their own serial enable line. In this manner, each device would receive the same clock and data signals, but only one device (the one to which the appropriate enable signal was sent) would be written to or read from at a time. This solution may work if there were very few devices on the OPU that were to be programmed. However, because this solution requires a separate serial enable line for each device to be programmed, this would also result in more wires than desired on the flex cable, especially as the number of programmable devices increased. Accordingly, there is still a need for a better way of being able to program multiple devices on an OPU using a common serial interface. Preferably, the number of lines on a flex cable should not be increased by the solution.